Biomass is generally composed of cellulose, hemicellulose, and lignin. The cellulose portion of biomass is particularly desirable in that this portion can be converted into individual sugar components, which can then be converted by microorganisms into various useful chemical compounds. As one example, the individual sugar components can be converted by microorganisms into ethanol, which can be used as a fuel or fuel additive for combustion engines.
The cellulose and hemicelluloses portions of the biomass are tightly bound to the lignin. Unless the cellulose and hemicelluloses are at least somewhat unbound from the lignin, conversion to individual sugar components, and into various chemicals by microbial action, can be highly inefficient. Biomass treatment processes such as dry milling, wet milling, steam explosion and ammonia fiber expansion (AFEX™—pending use and registration by MBI), however, have been used to unbind or break apart the various portions of the biomass, and thereby increase efficiency of conversion to individual sugar components, and ultimately to the various chemicals produced by microbial action.
U.S. Pat. No. 7,915,017 (Dale), for example, discloses a biomass treatment process that renders the structural carbohydrates of the biomass more accessible and/or digestible. The process uses ammonia to swell or rupture the biomass. The ammonia is recovered as ammonia vapor from an ammonia column, ultimately recycling the recovered ammonia in relatively dry form.
U.S. Pat. No. 5,171,592 (Holtzapple) discloses an ammonia biomass treatment process. The process includes recovery and recycle of the ammonia using superheated ammonia vapor to strip residual ammonia from the treated biomass.
AFEX™ type processes have been found to be quite effective in treating biomass. However, recovery of the various swelling agents used in those processes have been less than desirable in that substantial steps have been involved to recover the swelling agents for reuse. In order to increase efficiencies of the overall treatment process, it is therefore desirable to increase the efficiency of recovery and reuse of the swelling agents.